ADRIAN FLORIDO, HOST:
Days before the Super Bowl, a former NFL player was sent to prison for attempted murder. And he had a novel defense strategy. His lawyers blamed his actions on brain damage caused by football. It's a rare courtroom argument, but it's gaining traction nationwide, as NPR's Sacha Pfeiffer reports.
SACHA PFEIFFER, BYLINE: In a Boulder, Colo., courtroom yesterday, a prosecutor said Justin Bannan deserved 26 years in prison for shooting and injuring a woman. But two of his former NFL teammates pleaded for leniency. One of them, Mitch Unrein, sometimes wept.
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MITCH UNREIN: There is no doubt in my mind that Justin has lingering effects of concussions and CTE. Let's not just brush aside the many years of head trauma Justin has endured.
PFEIFFER: Justin Bannan got 16 years in prison anyway, but his case represents a new kind of legal battle. If former athletes or others have possible brain damage like CTE, chronic traumatic encephalopathy, which can cause mood swings, acting out, even violent behavior, is that a legitimate criminal defense?
Bannan isn't the only one who's tested the strategy in court. The trend hasn't gotten much notice, but individual cases have.
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UNIDENTIFIED PERSON: It started as a family cruise to Alaska and ended in death.
PFEIFFER: Kenneth Manzanares of Utah pleaded guilty to murdering his wife on that cruise ship, and his lawyer asked for a lighter sentence because she said he had possible CTE from high school sports.
In Pennsylvania, Judge Thomas Placey resigned after facing misconduct charges for abusive tirades on the bench.
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THOMAS PLACEY: Now. Now. Do you not listen?
PFEIFFER: And his lawyers said CTE caused by college sports concussions may be affecting his, quote, "impulsive behavioral control." This CTE-made-me-do-it approach has been used in just a handful of cases. But as CTE research evolves, Drexel University law professor Lisa Tucker expects it to become a more common legal strategy.
LISA TUCKER: Any good defense attorney is going to be looking for any kind of credible way to defend her client, and where there is brain injury, that absolutely should be considered a credible way.
PFEIFFER: She says in hindsight, this defense could have been used by former New England Patriots star Aaron Hernandez.
TUCKER: I'm not trying to say that Mr. Hernandez should have been acquitted altogether.
PFEIFFER: But she argues he should not have been convicted of first-degree murder because after Hernandez killed himself in prison, he was diagnosed with a severe case of CTE. Now, many people consider this legal defense a stretch. Kristen Dams-O'Connor is among those doubtful about a direct link between criminal acts and CTE.
KRISTEN DAMS-O'CONNOR: As a scientist, I can say that that is a gross oversimplification of what we currently know. That's where my skepticism comes in.
PFEIFFER: She directs the Brain Injury Research Center at Mount Sinai in New York and says it would be unfair for a court not to consider whether brain trauma affected a defendant's behavior. But she points out some people have CTE-like symptoms, yet no trace of CTE in their brains, and it takes an autopsy to diagnose CTE.
DAMS-O'CONNOR: So if you're making the case that CTE is the reason a person is behaving a certain way, that's very challenging to substantiate scientifically because we can't diagnose it during life.
PFEIFFER: This legal strategy is usually a version of an insanity defense. It hasn't been tested on many juries yet, but some lawyers say it's just a matter of time before it's widely accepted. After all, it took a while for battered woman defense and DNA evidence to become mainstream.
MARC CARLOS: And I think the same thing is going to be happening with CTE.
PFEIFFER: San Diego defense attorney Marc Carlos represented former NFL player Kellen Winslow in his multiple rape case and asked a judge for leniency due to possible CTE.
CARLOS: When we're able to examine people while they're alive, I think things are going to change, and people are going to realize that this is something that's very real.
PFEIFFER: But some judges so far appear unmoved. Carlos' client, Kellen Winslow, still got 14 years in prison. The man who killed his wife on the Alaska cruise got 30 years - quadruple the sentence his lawyer had hoped for. Here's his public defender, Jamie McGrady.
JAMIE MCGRADY: I think judges honestly are a harder sell because judges are always thinking long term about protection of the community.
PFEIFFER: So if they think a defendant may have incurable CTE, they may err on the side of a tough sentence rather than risk more violence and victims. In Justin Bannan's attempted murder case in Colorado, the judge gave him the mandatory minimum sentence of 16 years, even though prosecutors had asked for 26. So for now, CTE is an experimental defense. But expect to see more of this legal strategy as CTE science develops and NFL players get increasingly comfortable talking publicly about the lasting effects of head injuries.
Sacha Pfeiffer, NPR News. Transcript provided by NPR, Copyright NPR.
